18 research outputs found
Study of couplings effect on the performance of a spin-current diode: Nonequilibrium Green's function based model
In this paper, spin-dependent transport through a spin diode composed of a
quantum dot coupled to a normal metal and a ferromagnetic lead is studied. The
current polarization and the spin accumulation are analyzed using the equations
of motion method within the nonequilibrium Green's function formalism. We
present a suitable method for computing Green's function without carrying out
any self-consistent calculation. The influence of coupling strength and
magnetic field on the spin current is studied and observed that this device
cannot work as a spin diode under certain conditions.Comment: 9 pages, 3 figure
Thermoelectric effects in a double quantum dot system weakly coupled to ferromagnetic leads
Thermoelectric effects through a serial double quantum dot system weakly
coupled to ferromagnetic leads are analyzed. Formal expressions of electrical
conductance, thermal conductance, and thermal coefficient are obtained by means
of Hubbard operators. The results show that although the thermopower is
independent of the polarization of the leads, the figure of merit is reduced by
an increase of polarization. The influences of temperature and interdot
tunneling on the figure of merit are also investigated, and it is observed that
increase of the interdot tunneling strength results in reduction of the figure
of merit. The effect of temperature on the thermal conductance is also
analyzed.Comment: 13 pages, 4 figure
Exciton Spin Dynamics in Semiconductor Quantum Wells
In this paper we will review Exciton Spin Dynamics in Semiconductor Quantum
Wells. The spin properties of excitons in nanostructures are determined by
their fine structure. We will mainly focus in this review on GaAs and InGaAs
quantum wells which are model systems.Comment: 55 pages, 27 figure
Measurement of exciton spin coherence by nondegenerate four-wave mixing experiments in the chi((3)) regime
We demonstrate that the spin coherence relaxation of excitons can be measured in a three-beam four-wave mixing experiment in the chi((3)) regime, using a sequence of contracircularly polarized pulses. In contrast to other techniques like Faraday rotation measurement, our method allows one to access spin coherence without applying an external magnetic field. The superposition of opposite spin states (exciton-polariton spin coherence) is then probed in a nondegenerate configuration at the biexciton-exciton transition. Measurements are performed on a bulk CuCl platelet. The polariton effect is taken into account by modeling the propagation of the pulses. The exciton-polariton spin coherence time is demonstrated to be mainly determined by their spin lifetime